The present invention relates to a servomechanism for a reproducing system for a digitally recorded disk.
In a reproducing system for optically reproducing recorded information on a digitally recorded disk such as a digital audio disk or a video disk, the rotational drive of the disk is controlled by a spindle servomechanism, and the recorded information is read out by means of a pickup positionally controlled in the radial direction by a slider servomechanism.
Such a disk reproducing system also uses other servo-mechanisms, such as a focusing servomechanism for controlling the information detecting optical spot generated by the pickup so as to be correctly focused on the recording surface of the disk, a tracking servomechanism for controlling the optical spot so as to track accurately the recording track on the disk, namely, a helical recording track, and a time-axis servomechanism for correcting for time-axis (time-based) fluctuations in the reproduced signal. These focusing, tracking and time-axis servomechanisms are classified as "fine tuning" servo systems, whereas the aforementioned spindle and slider servomechanisms are classified as "rough tuning" servo systems.
In a system equipped with these various servomechanisms according to the prior art, signal processing, such as equalization of an error signal obtained in each servo system, is performed by a separate signal processor in each servo system. Hence, a large number of circuit elements is required, making the system complex and costly.